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Fix for the error codepath in ChildProcess

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This commit is contained in:
LemonBoy 2019-12-16 10:57:29 +01:00
parent c257f892fd
commit 9d9b0720f5
1 changed files with 30 additions and 11 deletions
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41
lib/std/child_process.zig
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@ -282,17 +282,36 @@ pub const ChildProcess = struct {
fn cleanupAfterWait(self: *ChildProcess, status: u32) !Term {
defer destroyPipe(self.err_pipe);
// Write maxInt(ErrInt) to the write end of the err_pipe. This is after
// waitpid, so this write is guaranteed to be after the child
// pid potentially wrote an error. This way we can do a blocking
// read on the error pipe and either get maxInt(ErrInt) (no error) or
// an error code.
try writeIntFd(self.err_pipe[1], maxInt(ErrInt));
const err_int = try readIntFd(self.err_pipe[0]);
// Here we potentially return the fork child's error
// from the parent pid.
if (err_int != maxInt(ErrInt)) {
return @errSetCast(SpawnError, @intToError(err_int));
if (builtin.os == .linux) {
var fd = [1]std.os.pollfd{std.os.pollfd{
.fd = self.err_pipe[0],
.events = std.os.POLLIN,
.revents = undefined,
}};
// Check if the eventfd buffer stores a non-zero value by polling
// it, that's the error code returned by the child process.
_ = std.os.poll(&fd, 0) catch unreachable;
// According to eventfd(2) the descriptro is readable if the counter
// has a value greater than 0
if ((fd[0].revents & std.os.POLLIN) != 0) {
const err_int = try readIntFd(self.err_pipe[0]);
return @errSetCast(SpawnError, @intToError(err_int));
}
} else {
// Write maxInt(ErrInt) to the write end of the err_pipe. This is after
// waitpid, so this write is guaranteed to be after the child
// pid potentially wrote an error. This way we can do a blocking
// read on the error pipe and either get maxInt(ErrInt) (no error) or
// an error code.
try writeIntFd(self.err_pipe[1], maxInt(ErrInt));
const err_int = try readIntFd(self.err_pipe[0]);
// Here we potentially return the fork child's error from the parent
// pid.
if (err_int != maxInt(ErrInt)) {
return @errSetCast(SpawnError, @intToError(err_int));
}
}
return statusToTerm(status);